Can body and method and apparatus for the production thereof

ABSTRACT

On a can body, including a can casing, which is closed around the can axis and includes a metal layer, and a closure part, which includes a metal layer, a laser connection is produced between the metal layers of the can casing and the closure part in an overlapping region of the closure part and the can casing. In at least one embodiment, the laser connection includes a plurality of perforations along the connecting line, or a plurality of narrowly delimited regions, in which the two metal layers are melted together. A plastic material is arranged on the laser connection. The laser connection ensures stability, and the plastic material ensures leak tightness, of the connection between the can casing and closure part.

The invention relates to a can body according to the introductory partof claim 1, to a method for the production of can bodies according tothe introductory part of claim 10 and to an apparatus for the productionof can bodies according to the introductory part of claim 13.

Aerosol can bodies are formed in one part or in several parts. Forone-part aerosol aluminum cans, a cylindrical can body is prepared bycold impact extrusion. Afterwards, a valve seat is formed at the openend by means of jolt necking. This method of production is veryexpensive due to the installation necessary for many processing stepsand due to the water and energy requirements for cleaning and drying.U.S. Pat. No. 4,095,544 and EP 0666124 A1 describe the production ofseam-less steel cans. In doing so, the cylindrical can body is producedby stamping, pressing and stretching from a steel sheet coated with tinor with plastic material. It has turned out that enormous problems occurwith forming a restricted can neck, because the material's structure haschanged and has hardened due to stretching.

Very dispread are also can bodies of steel sheet material, where theshell comprises a longitudinal welding seam. Bottom and the upperclosing are attached to the can shell via saddle joints. With saddlejoints, sealing problems can occur, which may be reduced using sealingrings. With the current thin-walled cans, problems will result with asealing arranged on the front side.

From WO 05/000498, a solution is known, where to a can shell, closed bya butt-jointed longitudinal laser seam, a can bottom is fixed at thelower front side by means of a laser seam. At the upper front side, arestriction is formed. To this end, a shaping roller is pressed fromoutside against the turning can shell. In the interior of the can shella support edge is arranged, which cooperates with the shaping roller andis moved during restriction in the direction towards the upper frontside. At the restricted end, a closing element comprising a valve seatis welded on. Optionally the upper end of the can shell is restricted byjolt necking or by spin flow necking, wherein this restriction can becarried out up to forming a valve seat. The valve seat is formed by thecan end deformed to the exterior, wherein the valve seat, in across-sectional plane which comprises the can's longitudinal axis, issubstantially circular. The free end extends from inside to outside andfrom outside back towards the exterior of the restricted can shell. Withthe valve seat, it is the matter of a so-called outward curl or anoutward edge flange.

From WO 05/068127, a solution is known, where a can shell, comprising abutt-jointed longitudinal laser seam, is pressed for shaping radial tothe exterior into an inner mold. At the lower front side of the canshell, a can bottom is welded on. At the upper front side, a closingelement including a valve seat is arranged by means of a laser seam.Optionally, a restriction process is carried out, such as jolt neckingor spin flow necking, instead of an upper closing element at the upperend. This restriction may be carried out up to forming the valve seat.The embodiments illustrated show outward curls or outward edge flanges.

It is the object of the present invention to find a solution by whichstable and tight cans can be produced in a simple and cost effectivemanner.

This object is achieved by, the characteristics of claim 1, of claim 10and of claim 13. The dependent claims describe preferred or alternativeembodiments.

For fixing a closing part arranged at the front side of the can wall,solutions are known from prior art, wherein a tight ring-shaped closedwelding seam is produced by means of a laser welding seam. It has beenshown that with such continuous laser welding seams, the contact areasof the two parts to be connected, which abut to each other, should haveno contamination and no coating. Otherwise, there is the risk thatportions of the contamination or coating explosively pass over intogaseous condition, due to the strong heat developing in the seam area,create interruptions of the seam and, thus, leaky sites. To overcomethis disadvantage, there is the task for any cans, to find a connectionby which no disturbances of the connection can by caused by smallcontaminations or by coatings.

For solving this problem, one has recognized in a first step that themetallic layer of the closing part and the laser connection betweenthese layers have only to guarantee stability of the can. Tightness witha laser connection can be achieved by a continuous inner coating or byplastic material, wherein the plastic material is tightly connected toboth parts.

In a second step, one has recognized that a laser connection includingmany interruptions along the line of connection and a plurality ofnarrowed areas, wherein the laser beam has molten the two metalliclayers, introduces less heat, and the risk of explosion-like developmentof gas is very much reduced.

This approach, comprising a plurality of narrowed metallic connectionpoints plus the tightening plastic material, can be used with all cansand closing elements having a metallic layer and, thus, is not limitedto aerosol cans and, of course, not to special aerosol cans exhibitingan inward edge flange.

A further advantage of such a circular laser connection showing a row ofnarrowed connection areas consists in that it can be carried out with alaser scanning apparatus. This means that the laser beam, for example bya moving mirror, is guided along the line of connection, wherein thelaser is alternately allowed to pass or is interrupted so thatconnections and interruptions are correspondingly created. Due to thescanning possibility, one can do without turning the can to pass overthe exit site of the laser beam. Even the laser exit head does not needto be moved along the line of connection.

If the can neck or the valve seat of an aerosol can is produced as aseparate part to be connected with a necked or restricted can shell, thewelding connection, according to a preferred embodiment, is carried outwith welding areas interrupted in peripheral direction, particularlywith point-shaped welding areas.

Such an interrupted welding connection can advantageously also be usedfor fixing the can bottom to the can shell. The can bottom can bepressed from the interior of the can against a restricted end region ofthe can shell, and can then be fixed in a slightly overlapping manner byan interrupted laser connection to the restricted region. If, forexample, there is no access from the end of the can shell opposite thecan bottom, so as to be able to bring the can bottom into the interiorof the can shell and then to the desired fixing region, there is thepossibility to bring a can bottom through the restriction, directly atits fixing region, into the interior of the can shell.

Since the radius of the can bottom is larger than the radius of theopening at the restricted fixing region of the can bottom, the roundcross-section of the can shell at the fixing region of the can bottom isdeformed into an oval free cross-section by a small pressure or by meansof squeezing. In doing so, the opening's cross-section enlarges in afirst direction and becomes smaller in a second direction perpendicularto it. If now the can bottom is tilted relative to the plane of the ovalopening, it can be introduced into the interior of the can shell, andcan be pressed from the interior against the restriction afterintroduction and after tilting it back. In the region of overlapping,the can bottom can be fixed to the can shell by a laser connectionhaving interruptions. With annular or disc-shaped plastic materialinside along the laser connection, a continuous and tight inner coatingcan be achieved.

In the case of longitudinal seams, the heat peak flowing with theformation of the seam results in undesired frazzling, where it can nolonger flow any further. This problem does not occur, if long continuouslongitudinal seams are formed and the can shells are severed from theemerging tube. Now it has been found that the problems in the productionof can shells from shell blanks or metal sheet can also be solved byforming a laser connection with many interruptions, instead of acontinuous laser seam, is formed along the line of connection. Theinterruptions prevent flowing together of a certain amount of heat and,therefore, heat spreading problems at the end of a connection or of ashell blank are excluded. Such a longitudinal can shell connectioncomprises a plurality of narrowed regions, wherein the laser beam hasfused the two overlapping metallic layers. If the material of the canshell is coated inside, and a continuous inner coating of the can shellis desired, plastic material is arranged in the interior of the can, andis tightly connected to the inner coating at the two sides of the seam.

According to another embodiment, the can shell with a formed valve seatis shaped by a radial enlarging pressing step at an inner mold, whereinthe inner mold, preferably, corresponds to a desired final shape of thecan shell. The inner mold can comprise any shape deviating from acylindrical one and can have décor structures. In doing so, the valveseat and, thus the can shell, is held into the inner mold duringpressing. The valve seat is not enlarged. By holding the can shell atthe valve seat, a defined position of the can shell relative to theinner mold is ensured. For pressing, an elastic press mandrel, to bebiased by a pressurized fluid, is introduced into the can shell.

When shaping in the inner mold, a shape can be formed at the free end ofthe can shell opposite the valve seat, which corresponds to theconnection region of a can bottom. The can bottom is subsequently fixedto the can shell by a laser connection.

According to another embodiment, the free end of the can shell,associated with the can bottom, is optionally only engaging its outermold, after the can bottom has been introduced. This procedure ispossible with all cans, where a can shell is connected to a can bottomduring production. For necking the can end after insertion of the canbottom, preferably a curling process is used. Therein, a rotating rolleris moved relative to the can shell around its circumference. At the canbottom introduced and held there, and preferably at the shaping rollertoo, the desired necking contour for the neck region of the can shell isformed. During rolling procedure, the can shell is tightly pressed tothe region of contact with the can bottom.

The marginal edge front surface of the can bottom is situated in theinterior of the can or inside the can, and the marginal edge frontsurface of the can shell is outside the can shell or at the exterior ofthe can. If the outer side of the can shell is provided with a décor,the décor extends downwards substantially down to the base surface.Therefore, the can is esthetically particularly appealing and differsfrom cans, where the region of curvature from a cylindrical shell to thecan's bottom is not provided with a décor.

In order that the shoulder-shaped, matching regions of the can bottomand the can shell, where the cross-section is reduced towards themarginal edge front side of the can shell, engage each other completelytightly, the can bottom, situated inside, can optionally be movedslightly in the direction of the can's axis towards the exterior, sothat the engaging region of the can shell is minimally expanded and isbrought into tight contact with the can bottom. In the region of thistight contact an annular closed laser connection between can shell andcan bottom can be applied.

Within the scope of the invention, it has been recognized that aperipheral laser seam between overlapping regions of the can bottom andthe can shell, particularly at the front side of the can shell does notneed to be tight. Preferentially, the peripheral laser seam has the taskto connect stably the can shell to the can bottom. Even with the innerpressure necessary for aerosol cans, the seam shall not burst. It hasbeen found that a stable connection, the tightness of which however isnot ensured, is achieved at distinctively smaller costs than anabsolutely tight peripheral laser seam. This is due to the fact that theperipheral laser seam is very narrow, for example having a width ofsubstantially 0.15 mm. If now a small contamination is in the area ofthe seam on one of the parts to be interconnected, an explosion-likevaporization of contamination portions, particularly fat or oil portionswill occur during welding. At these sites, short interruptions of theperipheral laser seam may result.

Since the can bottoms are preferably manufactured at a differentproduction location, in some cases using a production and shapingprocess which employs a lubricant, contaminations from the production orfrom transport can hardly be completely eliminated at justifiableexpenses. However, it is possible at smaller expenses to incorporate abarrier inside the can between the can bottom and the can shell, whichcloses the can's interior at the laser welding seam tightly against theoutside. Since with the possibly untight sites of the peripheral laserseam it is the matter of extremely small passages, the barrier does notneed to absorb large forces.

In order to be able to provide a tight barrier by small expenses betweenthe can shell and the can bottom, in the region of the peripheral laserseam or with a laser connection having a row of narrowed interconnectionareas, it is according to a further preferred inventive solution,claimed even independently from the independent claims as an invention,plastic material is arranged in the can's interior along the entireannular peripheral laser seam or laser connection, which is tightlyconnected to the can bottom and the can shell. In this way, any accessfrom the can's interior to the peripheral laser seam or to the laserconnection is excluded. The peripheral laser seam or the laserconnection ensures the necessary strength, while the plastic materialconnected to the bottom and the can shell guarantees tightness.

Plastic material can be applied as a ring or a disc with its ring marginalong the peripheral laser seam onto the can bottom, can be sprayed by anozzle or can be built up on the can bottom by an injection moldingstep. Prior to or after forming the peripheral laser seam, a tightconnection of the ring to the can shell, and optionally to the canbottom, is achieved at both sides of the peripheral laser seam.

The sealing plastic material along the peripheral laser seam between thecan bottom and the can shell can be particularly used in an advantageousmanner, if the can shell comprises inside a layer of plastic material,be it in the form of a coating or, as preferred, as a film. A can bottomcomprising plastic layer, which faces the can's interior, whichprotrudes towards the can's interior or upwards beyond the metallic edgeof the can bottom along the radial external edge may be introduced intoa cylindrical can shell having an inner layer of plastic material. Afterinsertion, a radial outer contact area of the layer of plastic materialof the can bottom engages the inner layer of the can shell.

Various embodiments and steps for assembling the areas of the can shelland the closing element are possible with the laser connection. This isconfirmed by the following examples.

If the can shell, in that end region where the can bottom is arranged,is slightly narrowed, the can bottom has a slightly larger outer radiusthan the passage opening of the can shell. If the round cross-section ofthe can shell is deformed in the fixing region of the can bottom with asmall pressure or by squeezing, to have an oval cross-section, theopening's cross-section enlarges in a first direction and becomessmaller in a second direction perpendicular to the first one. The canbottom is tilted relative to the plane of the oval opening slightlyabout an axis, which is substantially parallel to the first direction,and is then introduced into the interior of the can shell. Afterinsertion, it will be tilted back and is pressed against the restrictionin the interior of the can shell. In the overlapping region, the canbottom can be fixed to the can shell by a laser connection. Withring-shaped or disc-shaped plastic material inside along the laserconnection, a continuous and tight inner coating can be achieved.

As has been described above, the end region of the can shell can bedeformed in a deforming step to match with a shoulder-shaped contactsurface of the can bottom and can be fixed by a peripheral laser seam.In a heat treatment step, the layer of plastic material of the canbottom is connected to the inner layer of the can shell in the region ofcontact. To this end, the layer of plastic material of the can bottomcomprises optionally a sealing material at least in the area of theconnection desired. The heat treatment step is optionally carried outprior to the deformation step so that the can bottom adheres alreadyslightly to the can shell already during deforming.

If one should do without a deformation of the can shell at the canbottom after introducing the same, a receiving area in form of an ringgroove can be formed for a corresponding contact area of the can bottomwhich protrudes to the exterior. The can bottom should be pressed fromoutside and from below against the can shell so that the contact area ofthe can bottom reaches the receiving area of the can shell and is heldin it. Now a ring groove area of the can bottom convex from the exterioris in a ring groove area of the can shell, which is concave from theinterior. The marginal edge front surface of the can bottom is in theinterior of the can or at the inner side of the can, and the marginaledge front surface of the can shell is outside the can shell or at theexterior of the can.

At the free lower end of the can shell, i.e. at the can bottom, thecross-section of the can shell increases slightly in upwards direction,and is reduced again. The lower restriction of the cross-section has tobe very small so that the can bottom, with the maximum outer diameter,can be pressed into the interior of the can shell. When pressing it in,the shell region at the lower restriction of the cross-section willelastically slightly expand and/or the can bottom, at its maximum outerdiameter, will be slightly narrowed. With the can bottom pressed in, ashoulder of the can bottom engages a corresponding shoulder of the canshell along the entire circumference. In this shoulder region, thecross-section of the free end of the can shell is reduced so that anabutment is formed. The peripheral laser seam will be formed in acircular closed manner along the shoulder regions being pressed againsteach other. After the restricted shoulder region, the diameter of thecan shell increases again. From the exterior a deepened groove will beseen at the shoulder region and directly above it.

It is advantageous, if the contact area of the can bottom is introducedinto the interior of the can shell. The thickness of the can bottom ismostly chosen slightly larger than the thickness of the can shell.Correspondingly, the shoulder area of the can bottom is slightly morestable in shape than the shoulder area of the can shell. An optimumpress fit is achieved, if the more stable shoulder area is pressed frominside against the slightly less stable shoulder area. The outershoulder area is optionally slightly stretched in circumferentialdirection, but the inner and more stable shoulder area will not bedeformed and not be jolted. If the can shell were inside and the morestable can bottom were outside, jolt wrinkles could develop in the canshell due to the pressing force, which would prevent a tight peripherallaser seam.

In order to ensure a continuous inner coating at the transition from thecan shell to the can bottom, the can bottom is coated inside and isprovided with a meltable sealing bead. The can shell is coated with afilm, wherein no coating is provided in the shoulder area for theconnection with the can bottom. The outer side of the can bottom, whichis opposite the can's interior, has no coating at least in the shoulderarea. The peripheral laser seam is now formed between the directlyengaging metallic areas of the can shell and the can bottom. To coat themarginal edge front surface of the can bottom, which is situated in thecan's interior, and the uncoated area of the can shell joining to it,the meltable sealing bead is heated and is, thus, caused to flow andsubsequently to solidify, so that the material of the sealing bead formsa complete connection between the inner coatings of the can shell and ofthe can bottom.

In order to provide a protective coating at the bottom side of the can,an outer bottom cover, preferably in the form of a plastic bottom, isattached to the lower can end. If the bottom cover extends slightly fromthe can bottom along to the can wall, it can engage the deepened groovedirectly above the peripheral laser seam. Thus, the bottom cover coversthe lower marginal edge front surface of the can shell and theperipheral laser seam. If the bottom cover is tightly connected to thecan shell at the deepened groove and the can wall comprises an outerfilm, the metallic layer of the can shell and of the can bottom istightly closed towards the exterior and oxidation problems can beexcluded. Since the bottom cover, preferably, extends over the entirecan bottom, an outer coating of the can bottom can be omitted.

The various processing steps can be effected on turntables which,however, is relative expensive due to the synchronized handing over anddue to the holding and transferring elements matching the can diameter.The performance of throughput can advantageously be achieved with asolution, where several linear processing lines are provided inparallel. In front of the individual processing stations, storage areascan be foreseen, from which the can bodies, being partly assembled, aredirected to the parallel processing lines. If the production is changedfrom cans having a first diameter to cans having a second diameter,there are only few elements in the parallel linear processing lineswhich have to be adapted to the changed diameter.

By the inventive process steps, it is possible to produce cans havingvery thin can shells. For producing the can shells, steel sheet materialof a thickness of substantially merely 0.16 mm can be used. Optionally,even metal sheet of a thickness between 0.16 and 0.12 may be used.

With a can body according to the invention, comprising a can shellclosed around a can axis and including a metallic layer, and a closingpart including a metallic layer, a laser connection is formed betweenthe metallic layers of the can shell and of the closing part in theoverlapping area of the closing part along a line of connection. Thelaser connection comprises many interruptions along the line ofconnection and a plurality of narrowed areas, where the two metalliclayers are interconnected. At the laser connection, plastic material isarranged. The laser connection ensures stability, and the plasticmaterial ensures tightness of the connection between the can shell andthe closing part.

In the process according to the invention for the production of a canbody according to the invention, a laser connection having manyinterruptions is formed between the metallic layers of the can shell andthe closing part along the line of connection and a plurality ofnarrowed areas, where the two metallic layers are fused together. At thelaser connection, plastic material is arranged, wherein the laserconnection ensures stability, and the plastic material ensurestightness. The areas where the two metallic layers are fused together,are preferably processed with a laser scanning device, wherein the laserbeam is guided, for example by mirror movements, along the line ofconnection or along the overlapping area, and is alternately emitted orinterrupted so that interconnections and interruptions are created.

An apparatus according to the invention for the production of a can bodyaccording to the invention comprises a laser welding device and aholding device for holding the can shell and the closing part, whereinthe laser welding device includes a laser scanning device, which fusesthe two metallic layers together in a plurality of narrowed areas by ascanning laser beam. The laser scanning device comprises a control unit,a laser source, which provides the scanning laser beam for the desiredtime periods, and at least two mirrors or reflection surfaces rotatableabout two axes perpendicular to one another, wherein the scanning laserbeam from the laser source reaches the respective desired site of theoverlapping area via the two rotatable mirrors or reflection surfaces,while the holding device holds the can shell and the closing part in afixed position.

The drawings elucidate the solution according to the invention withreference to embodiments. It is shown in

FIGS. 1 a, 1 b, 1 c vertical cross-sections of the connection of theupper closing part together with the can shell,

FIG. 1 d a detail in a plan view onto the connection of the upperclosing part with the can shell,

FIG. 2 a schematic illustration of an apparatus for connecting the upperclosing part to the can shell,

FIG. 3 a schematic illustration of a scanning laser device for forming acircular laser connection,

FIG. 4 a a vertical cross-section of a detail of the connection of thecan bottom to the can wall,

FIG. 4 b a plan view of a detail of the connection of the can bottom tothe can wall,

FIGS. 5 a, 5 b, 5 c vertical cross-sections of the can shell and the canbottom during insertion of the can bottom,

FIGS. 6 a, 6 b, 6 c schematic plan views of the can shell and the canbottom during insertion of the can bottom,

FIG. 7 a front side view of a can shell produced from sheet material bymeans of a laser connection,

FIG. 7 b a lateral view of a can shell produced from sheet material bymeans of a laser connection,

FIGS. 8 a, 8 b enlarged details of vertical cross-sections of the laserconnection of the can shell,

FIGS. 9 a and 9 b vertical cross-sections of a detail of the connectionof the can bottom to the can wall, and

FIG. 10 a vertical cross-section through a beverage can, whereinalternative embodiments are represented at left and at right, where thepositions of the can shell and the closing part are different in theoverlapping area.

FIGS. 1 a, 1 b, 1 c and 1 d show the upper end, restricted to a neckportion 4, of a can shell 3, held by a holding device not shown. On theinner side of the can shell 3 is arranged an inner film 3 b, and on theouter side is an outer film 30 or an outer coating. From below, aholding mandrel 34 lifts the upper closing part 33 towards the upperopening of the can shell 3. The upper closing part 33 comprises a valveseat 5 with an inward edge flange 6 and with a sealing ring 7 insertedinto the inward edge flange 6. In order to ensure precise positioningand pressing of the upper closing part 33 against the neck portion 4,the holding mandrel 34 comprises a centering projection 34 a and a presssurface 34 b. The upper closing part 33 with its overlapping area 33 a,adapted to the necking of the can shell 3, is pressed by the presssurface 34 a against the corresponding surface of the neck portion 4.

To connect the upper closing part 33 firmly and tightly to the can shell3, an upper press ring 36 is put from above onto the neck portion 4. Aheating device 36 a is formed and arranged in such a manner that heatcan be directed from the outer connection area 35 b of plastic material7 a, wherein a hot sealing connection is formed between the upperconnection area 35 b of the plastic material 7 a and the inner film 3 b.If the plastic material 7 a is formed in one piece with the sealing ring7, a continuous inner coating is created from the inner film 3 b up tothe sealing ring 7.

The metallic layer of the can shell 3 is connected to the metallic layerof the upper closing part 33 in the overlapping area 33 a by a scanninglaser beam 37. The generated laser connection comprises in theoverlapping area 33 a a plurality of narrowed connecting points 38,where the laser beam has fused the two metallic layers together. It hasturned out that the material of the inner film 3 b, by bringing in laserenergy in a point-shaped manner, goes away from the center of the laserbeam, and the two metallic layers interconnect with one another withoutany disturbance via bolt-shaped fusion areas 39 fused into one anotherand solidified. Time and power, with which the laser beam produces aconnection point 38 is chosen in a way that the fusion area 39 does notpass completely through the metallic layer of the upper closing part 33and the plastic layer 7 a is not affected. Various grids and,optionally, various cross-sectional shapes of connection points arepossible, at least one row along the periphery being necessary. Bycontrolling the scanning laser, the arrangement and the shape of theconnection areas or of the connection points may be changed at smallexpenses.

FIG. 2 shows an embodiment of an apparatus for connecting the upperclosing part to the can shell. In a continuously moving chain or banddevice 40, protruding holding mandrels 34, including a centeringprojection 34 a and a press surface 34 b, are mounted, wherein severalrows of holding mandrels 34 may be arranged side-by-side to provideseveral can shells 3 in parallel with upper closing elements 33. In afirst loading space 42, upper closing elements 33 are put onto theholding mandrels. In a second loading space 43, the can shells 3 are putonto the holding mandrels 34 over the upper closing elements 33.

An upper press ring 36 is put from above onto the neck portion 4 of thecan shell 3 and achieves with a heating device a sealing connection ofthe connection area 35 b of the plastic material 7 a to the inner filmof the can shell 3. Afterwards the metallic layer of the can shell 3 isconnected to the metallic layer of the upper closing part 33 by ascanning laser beam 37. Since the can parts do neither need to berotated nor has the laser source to be circularly moved, the laserconnection can be built up in a simple manner. In a dispensing area 45,the can shell 3 together with the upper closing part 33 are dispensedfor conveying them to a further can processing station.

FIG. 3 shows a laser scanner device 46, which forms, along a circularline by the scanning laser beam 37, a laser connection comprising aplurality of narrowed areas, in which the laser beam has fused twometallic layers. In the treatment step shown, a can bottom 13 is pressedfrom the interior against a lower restriction of the can shell 3, and isfixed by the laser connection. In the can's interior a holding mandrel34′ presses the can bottom 13 against the restriction of the can shell3, while the can shell 3 is held by the press ring 36 against the canbottom 13.

The scanning laser beam 37 from a laser source not shown reaches thecircular area, where the laser connection shall be formed, via twomirrors 47 or reflection surfaces rotating about axes perpendicular toeach other. A control unit not shown and two drives 48 determine therotational position of the two mirrors 47.

It goes without saying that instead of the can bottom, a differentclosing element could be attached to the can shell 3 by the scanninglaser device 46. In addition, the closing element could also be arrangedon the front outside. This solution is, thus, not limited to aerosolcans and, of course, not to special aerosol cans exhibiting an inwardedge flange.

FIGS. 4 a and 4 b show a laser connection produced by the scanning laserdevice 46. It comprises in the overlapping area of the interconnectedparts a plurality of narrowed connection points 38, where the laser beamhas fused the two metallic layers together. It has turned out, that thematerial of the inner film 3 b, by bringing in laser energy in apoint-shaped manner, goes away from the center of the laser beam, andthe two metallic layers interconnect with one another without anydisturbance via bolt-shaped fusion areas 39 fused into one another andsolidified. Various grids of connection points are possible, at leastone row along the periphery being necessary. By controlling the scanninglaser, the arrangement and the shape of the connection areas or of theconnection points may be changed at small expenses.

The can shell 3, at the can bottom 13, is slightly restricted to form ashoulder. The can bottom 13 has a correspondingly shaped overlappingarea, which is firmly welded by the laser connection to the restrictedarea of the can shell 3. In the can's interior, along the circular laserconnection, plastic material 15 is arranged that is tightly connectedalong a lower connection area 15 a to the can bottom 13 and along anouter connection area 15 b to the can shell. The plastic material 15 maybe put as a ring or as a disc with a ring margin onto the can bottom 13,can be sprayed by a nozzle or can be built up on the can bottom 13 by aninjection molding step. If a central covering area of the plasticmaterial 15 covers the middle area of the can bottom 13, a can body maybe produced at small expenses, the entire inner surface of which has aplastic coating.

The lower end region of the can shell 3 is tightly engaging theoverlapping area of the can bottom 13, which is shoulder-shaped incross-section. The peripheral marginal edge front surface of the canbottom 13 is in the can's interior or at the inner side of the can, andthe lower marginal edge front surface of the can shell 3 is outside thecan bottom 13.

FIGS. 5 a, 5 b and 5 c as well as 6 a, 6 b and 6 c show how to introducea can bottom 13 through the restricted end region of the can shell 3. Asthe can shell 3 is slightly restricted in the end region where the canbottom 13 will be arranged, the can bottom 13 has a slightly largerouter radius than the passage opening of the restricted region.

In FIGS. 5 b and 6 b, the cross-section of the can shell 3 is deformedto an oval cross-section by small pressure or by means of squeezing. Indoing so, the opening's cross-section enlarges in a first direction andbecomes smaller in a second direction perpendicular to the first one.The can bottom 13 is held by an introducing holder 49, whereinpreferably a sub-pressure is created for holding in a suction contactarea 49 a. When introducing, the can bottom 13 is slightly tilted by theintroducing holder 49 relative to the plane of the oval opening about anaxis, which extends substantially parallel to the first direction. Inthis tilted position, the can bottom 13 is introduced into the interiorof the can shell 3.

FIGS. 5 c and 6 c show a situation after the can bottom 13 has beentilted back by orienting the introducing holder 49 vertically. To pressthe can bottom 13 from the interior against the restriction, even afterthe introducing holder 49 has been removed, the upper front surface ofthe holding mandrel 34′ presses against the can bottom. In theoverlapping area, the can bottom 13 can be fixed to the can shell 3 by alaser connection. The novel and inventive laser connection, claimed evenindependently from the independent claims as an invention, including aplurality of narrowed areas, where the laser beam has interconnected thetwo metallic layers, cannot only be advantageously used for connecting aclosing element to the can shell 3. Referring to FIGS. 7 a, 7 b and 8 a,8 b a can shell 3 is described which is produced from sheet material bya laser connection. The sheet material is deformed to a tube, whereinthe two lateral regions associated to each other engage each other in anoverlapping manner in then overlapping area 50.

With tightly engaging lateral areas, a laser connection 51 is formed bya laser, this connection consisting of a plurality of narrowedconnection areas. In doing so, either the can shell 3 may be movedrelative to a laser emission site, or the site of impingement of ascanning laser beam 37 is moved along the overlapping area 50.

In case, the inner space of the can shell 3 has not to be separatedcompletely from the metallic layer of the can shell 3, a connectionaccording to FIG. 8 a is sufficient, where a front side, situated in theinterior, of the metallic can shell layer is accessible from theinterior of the can.

To be able to ensure a complete inner coating, an inner film 3 b or aplastic coating is arranged on the metallic layer of the sheet materialfor the can shell 3, and on the first front side, which will be situatedin the interior of the can shell 3, a plastic bead 52 is arranged. Afirst connection surface 52 a of the plastic bead 52 is directlyconnected to the inner film 3 b or to the coating at the first frontside by a sticking or sealing connection. After forming the can shell, asecond connection surface 52 b of the plastic bead 52 engages the innerfilm 3 b in vicinity of the second front side of the metallic layer ofthe sheet material. The second connection surface 52 b too is tightlyconnected to the inner film 3 b or the coating by a sealing or stickingconnection. Can shell having this connection may advantageously be usedwhen producing tripartite cans. Tripartite cans comprising a can shell,which has a longitudinal laser connection 51 exhibiting a plurality ofnarrowed connection areas and a plastic bead 52 being tightly connectedto the inner film 3 b or a coating can be produced in a simple mannerwith high quality.

FIG. 9 a shows a laser connection between a can shell 3 and a can bottom13, which is produced by the scanning laser device 46. It comprises aplurality of narrowed connection points 38 in the overlapping area 53 ofthe two interconnected parts 3, 13, where the laser beam has fusedtogether the two metallic layers of the can shell 3 and the closing partor the can bottom 13.

The overlapping area 53 is annularly closed and extends incross-sectional planes, which comprise the can axis 2, preferably underan angle in the range of 5° to 85°, particularly of 20° to 70°, morepreferably, however, of 30° to 60° with respect to the can axis 2. Inthis way, tight engagement of the two parts to be connected can beachieved by a pressing force acting between the two parts in theoverlapping area 53. In these cross-sectional planes, the can shell 3extends at the overlapping area 53 from one side up to its marginal edgefront surface 3 c at one end of the can shell 3. The outer marginal areaof the closing part extends at the overlapping area 53 from one side upto the radial outer marginal edge front surface 13 c closing part or ofthe bottom 13. In the overlapping area 53, the can shell 3 and theclosing part have substantially the same shape, so that a respectivelayer engages the other one without any gap. In the embodimentillustrated, the two parts comprise only one layer in the overlappingarea.

The plastic material necessary for tightness at the laser connection isformed by an outer coating 54 of the can bottom 13. For tightlyconnecting the outer coating 54 both to the can bottom 13 and the canshell 3 in the overlapping area or at the laser connection, preferably aheat treatment is effected in the overlapping area. To be able to ensurea consistently tight connection of the outer coating 54 to the can shell3, the outer coating 54 comprises a sealing layer to be connected to thecan shell 3 at least at the overlapping area, and the connection of theouter coating 54 to the metallic layer of the can bottom 13 is also afirm and tight connection. The outer coating 54 forms a corrosionprotection at the can bottom 13, which is advantageous with cans ofsteel, because they do not oxidize when put on a wet surface.

It has been found, that the material of the outer coating 54 goes awayfrom the center of the laser beam, when bringing in laser energy in apoint-shaped manner, and the two metallic layers interconnect with oneanother without any disturbance via bolt-shaped fusion areas 39 fusedinto one another and solidified. Around the solidified fusion areas 39,the outer coating 54 remains as a sealing layer extending around alongthe overlapping area 53, thus achieving the desired tightening function.Various grids of connection points 38 are possible, at least one rowalong the periphery being necessary. By controlling the scanning laser,the arrangement and the shape of the connection areas or of theconnection points 38 may be changed at small expenses.

In the embodiment illustrated in FIG. 9 a, neither the can bottom 13 orthe closing element, nor the can shell 3 is coated on the can's innerside. Such cans without an inner coating may be used for all products,where no undesirable reactions between the metallic layer of the closingelement or of the can shell 3 and the product are expected which, forexample, is the case with polyurethane foams for constructionapplications.

The realization of the laser connection illustrated in FIG. 9 a may bechosen in an analogous way for the upper closing element, in which casethe upper closing element or, optionally, the can shell 3 comprises aplastic coating at least in the overlapping area 53.

FIG. 9 b shows an embodiment of the connection between the can shell 3and a closing part, particularly a bottom 13, in which connection theradial outer marginal edge front surface 13 c of the part situatedinternally is not accessible from the can's interior, because a marginalregion is folded over by 180° to the exterior at the radial externalmarginal edge front surface 13 c. If the folded marginal region is madeto engage the other part, the marginal edge front surface 13 c, afterforming the laser connection or the connection points 38, is no longeraccessible. If the can shell 3 comprises an inner film 3 b, and theclosing part or the can bottom 13 comprises an inner coating 13 d, acontinuous inner coating is provided, and the plastic material of theinner film 3 b and of the inner coating create tightness. It goeswithout saying, that the end region of the can shell too can be foldedto the exterior in a corresponding manner, if the closing part isengaging the can shell 3 from outside.

FIG. 10 shows an embodiment in the form of a beverage can 55, where thecan bottom, together with the can shell 3, is formed as a deep-drawn,cup-shaped part. At the upper, open end of the can shell 3, the upperclosing part 56 is arranged with a tear-off can top device 57. The laserconnection between the can shell 3 and the upper closing part 56comprises a plurality of narrowed connection points 38, where the laserbeam has fused together the two metallic layers of the can shell 3 andthe upper closing part 56.

For bringing the can shell 3 and the upper closing part 56 together inthe overlapping area 53, there are two possibilities. Either the upperclosing part 56, in an analogous way as in the process represented inFIGS. 5 a, 5 b and 5 c, is brought into contact in the overlapping area53 from the can's interior (left side), wherein the pressing force hasto be achieved by a introducing holder. To enable pressing from theinterior, the introducing holder has to be connected to the upperclosing part 56 either by a sub-pressure or by a clamping device,because at the can bottom, there is no access to the can's interior. Thesecond possibility of assembling consists in that the upper closing part56, in the overlapping area 53 is brought into contact to the can shell3 from the can's exterior (right side), wherein the two parts to beinterconnected can respectively be pressed against each other from theexterior. In both variants, the can shell 3 and the upper closing part56 are formed in such a way in the overlapping area, that the outercontour corresponds to a desired shape of a beverage can.

The plastic material required for tightness of the laser connection,according to the left illustration, is formed by an inner coating orinner film 3 b of the can shell 3, the inner film 3 b or the innercoating being situated in the overlapping area between the can shell 3and the upper closing part 56. For a tight connection of the inner film3 b or of the inner coating both with the upper closing part 56 and thecan shell 3 in the overlapping area or at the laser connection, a heattreatment is preferably carried out in the overlapping area. Inparticular, the inner film 3 b or the inner coating comprises a sealinglayer facing the upper closing part 56 in the overlapping area.

The plastic material required for tightness of the laser connection,according to the right illustration, is formed by an inner coating 58 oran inner film of the upper closing part 56, the inner coating 58 or theinner film being situated in the overlapping area between the can shell3 and the upper closing part 56. For a tight connection of the innercoating 58 both with the upper closing part 56 and the can shell 3 inthe overlapping area or at the laser connection, a heat treatment ispreferably carried out in the overlapping area. In particular, the innercoating comprises a sealing layer facing the can shell 3 in theoverlapping area 53.

When bringing in laser energy in a point-shaped manner, the inner film 3b or the inner coating 58 goes away from the center of the laser beam,and the two metallic layers interconnect with one another without anydisturbance via the bolt-shaped solidified fusion areas 39. The innerfilm 3 b or the inner coating 58 forms a continuous sealing in theoverlapping area. It goes without saying, that tightness may be achievedor increased also, or in some cases in addition, by plastic materialarranged at the can's inner side, which is connected to the inner film 3b and the inner coating 58, in an analogous way to the explanations inaccordance with FIGS. 1 c and 4 a.

To prevent parts with an inner coating and/or an inner film to exposurefreely the metallic layer of the can shell 3 or of the upper closingpart 56 in the can's interior, a marginal edge front surface of one ofthe interconnected parts should be coated in the can's interior.Correspondingly, at the left side, a radial external marginal edge frontsurface 56 c of the upper closing part 56 is coated, In the embodimentaccording to the right side, a terminal marginal edge front surface 3 cis coated at the free end of the can shell 3.

1. Can body comprising: a can shell closed around a can axis, whichincludes a metallic layer, and a closing part, which includes a metalliclayer, wherein in an overlapping area of the closing part and the canshell a laser connection is formed between the metallic layers of thecan shell and the closing part along a line of connection, wherein thelaser connection comprises many interruptions along the line ofconnection and a plurality of narrowed areas, in which the two metalliclayers are fused together, and a plastic material is arranged at thelaser connection, and wherein the laser connection ensures stability,while the plastic material ensures tightness.
 2. Can body according toclaim 1, wherein the areas, where the two metallic layers are fusedtogether, are formed as narrowed metallic connection points.
 3. Can bodyaccording to claim 2, wherein the connection points form at least onerow along the line of connection, in particular being arranged in theshape of a grid.
 4. Can body according to claim 1, wherein the closingpart is an upper closing part, particularly including a valve seat, butoptionally including a tear-off can top device for a beverage can. 5.Can body according to claim 1, wherein the closing part is a can bottom(13).
 6. Can body according to claim 1, wherein the plastic material isarranged in the form of a coating or of a film at least on the closingpart or on the can shell in the overlapping area and is situated betweenthe two interconnected metallic layers.
 7. Can body according to claim1, wherein an inner film is arranged on the inner side of the can shell,the material of the inner film being situated between the two metalliclayers in those areas, where the two metallic layers are fused together,is displaced by bringing in laser energy in a point-shaped manner, andthere are formed solidified fusion areas of the two metallic layers. 8.Can body according to claim 1, wherein plastic material is arranged inthe can's interior along the entire laser connection and is tightlyconnected to the closing part and the can shell.
 9. Can body accordingto claim 8, wherein the plastic material is arranged in the form of aring or a disc on the can bottom, and is connected to the can shellradial outside.
 10. Method for the production of a can body comprising acan shell closed around a can axis, which includes a metallic layer, anda closing part, which includes a metallic layer, wherein in anoverlapping area of the closing part and the can shell a laserconnection is formed between the metallic layers of the can shell andthe closing part along a line of connection, the method comprising:forming the laser connection is formed with many interruptions along theline of connection and a plurality of narrowed areas, in which the twometallic layers are fused together, and a plastic material is arrangedat the laser connection, wherein the laser connection ensures stability,while the plastic material ensures tightness.
 11. Method for theproduction of a can body according to claim 10, wherein the areas, wherethe two metallic layers are fused together, are arranged as narrowedmetallic connection points in at least one row along the line ofconnection, but in particular in the shape of a grid.
 12. Method for theproduction of a can body according to claim 10, wherein the areas, wherethe two metallic layers are fused together, are formed by a scanninglaser device, wherein the laser beam, is guided along the lone ofconnection or along the overlapping area and is alternately emitted orinterrupted so that connections and interruptions are created. 13.Apparatus for the production of a can body comprising a can shell closedaround a can axis, which includes a metallic layer, and a closing part,which includes a metallic layer, and a laser connection, which is formedbetween the metallic layers of the can shell and the closing part in anoverlapping area of the closing part and the can shell along a line ofconnection, the apparatus comprising: a laser welding device; and aholding device for holding the can shell and the closing part, whereinthe laser welding device includes a scanning laser device, which fusesthe two metallic layers together in a plurality of narrowed areas by ascanning laser beam.
 14. Apparatus for the production of a can bodyaccording to claim 13, wherein the scanning laser device provides acontrol, a laser source, which provides the scanning laser beam for thetime periods desired, and at least two mirrors or reflection surfacesrotating about axes perpendicular to each other, wherein the scanninglaser beam from the laser source reaches the respective desired site ofthe overlapping area via the two rotating mirrors or reflectionsurfaces, and the holding device holds the can shell and the closingpart in a fixed position.